Gelling properties of a κ/ι hybrid carrageenan: effect of concentration and steady shear
2007
The gelling properties of κ/ι hybrid carrageenans extracted from Portuguese seaweeds have been studied for various concentrations and shear conditions. The gel equilibrium storage modulus in 0.05 m KCl shows a power law dependence with the biopolymer concentration. Data analysis with a fibril model indicates that the fractal dimension of networking fibrils differ from the one displayed by pure κ- or ι-carrageenan fibrils. κ/ι hybrid carrageenan gels show thermal hysteresis reminiscent from κ-carrageenan gels under similar salt conditions. Application of steady shear rate during the cooling of a hot κ/ι hybrid carrageenan solution impedes the gel formation. However, a shear-rate-dependent gel structural rebuilding is observed after shear cessation. Shear-processed gels are softer and show a depressed melting temperature when compared with gels formed under quiescent conditions. These experimental results are compared with data obtained with pure κ-carrageenan and pure ι-carrageenan solutions under similar steady shear and salt conditions.
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